Fibrous cellulose mass and chemical reaction therewith



Patented Dec. 24, 1935 UNITED smrsi iill.

r o FicE FIBROUS CELLULOSE MASS AND CHEl /HCAL REACTION THEREWZTH Delaware No Drawing. Application-March 28, 1932, Serial No. 601,711

13 Claims.

The present invention relates to the treatment of cellulose fibers, particularly the isolated fibers of wood cellulose, as compared tothe fibers of cotton cellulose. It is particularly valuable for 5 esterification processes, such as nitration. Little difficulty is experienced in the nitration of cotton linters, and the practice is well established. I refer particularly to that part of the process where the cellulose, such as cotton lintl ers, is introduced into the acid for effecting the reaction. Uniform and complete penetration of the cotton mass is essential, and the requirements are more urgent the shorter the time permitted for the nitration process.

15 Cotton linters have an ability to mat into loose fluffy masses which are easily penetrated by acid so that uniform nitration is effected. When wood cellulose fibers are similarly treated, it has been found that the physical form of the mat or mass introduced into the acid has a pronounced effect upon the completeness and uniformity of nitration of all the fibers. Unless all the fibers are uniformly nitrated the product may contain. lower nitrated forms, or unnitrated fibers, or incompletely nitrated fibers.

This condition is not obvious until solutions are made, and it is not possible or practical to remove the defective material. The defect must be prevented. The product may be useless or of low grade unless complete nitration and uniform nitration of all fibers is effected.

Although the invention is useful with cotton fibers as well as with wood fibers, or chemical wood pulp, it is more advantageous with the latter than with the former. Cotton fibers grow as such per se, and have a twist in them by reason of which they are somewhat kinky. Cellulose fibers of wood and other material grow in bundles, and are straighter; and by means of the processes of liberation or fibration, especially in preparing chemical cellulose, they become more flexible as straight fibers, thereby matting more easily than cotton into compact masses.

The application of W. C. Wilson, Serial No. 184,435, filed April 16, 1927, now Patent No. 1,925,162, issued Sept. 5, 1933, discloses one method of preparing the chemical fibers of wood cel- I cannot be greatly compressed for shipment or transportation, without becoming so compacted and matted that the efiects desired are not obtained.

The present invention aims to provide a form 5 of massed fibers, particularly the chemical fibers, such as from wood, which form is not amorphous in the sense used for the Wilson process; which may be compressed for transportation and shipment; and which may be introduced into a liquid, 10 such as an acid, or subjected to other fluid chemical reagent so that rapid and complete penetration is effected to produce uniformity in the reaction product. The process generally comprises forming a mat containing the fibers, adherently united to form a bibulous, spongy coherent distended fibrous mass, and subjecting the mass or mat, or fragments thereof to a liquid or other fiuid reaction mixture.

Various materials are employed to react with cellulose for making cellulose derivatives, with preservation of the initial megascopic form, or fibrous identity, of the fibers. Caustic alkali solution is used to make alkali cellulose, and to mercerize the fibers. Sulphuric acid is used. Mixtures of sulphuric acid and nitric acid are used to make nitrocelluloses of various degrees of nitration. Sulphuric acid mixed with acetic anhydride is used to make cellulose acetate. Various times of reaction are required for specilied results, and it is important that all the fibers be uniformly subjected to the same action for the specified time.

Among the nitration processes, that which is described in the application of W. C. Wilson, Serial No. 119,995, filed July 1, 1926, now Patent No. 1,883,215, is a short-time process, and is the one in particular for which this invention has been developed. It is one in which much difliculty has been experienced in using wood cellulose as the raw material, especially where the pulp is prepared in one place and shipped to another for nitration. However, the invention is not to be considered as limited tothis or any other nitration process, but it is to be considered as applicable to other processes, as hereinabove stated.

There are numerous ways of forming fibers into a mat, but these are not broadly claimed.

' as this invention, although certain improvements in some of the old processes are a part of this invention.

One method of felting fibers, especially short cellulose fibers of wood, into a mat of the characterdescribedis found in the U. S. Weiss Pat- 10f pulp.

outs No. 1,336,402 and 1,336,403. It consists of moving fibers, as by showering them, onto a table, and spraying adhesive onto the fibers. The wetted fibers pile up into a loose fiuffy mass and the adhesive unites the fibers together. Any adhesivehmay be used. However, for this invention I may relate the adhesive to the esterification process for which the fibers 'are matted. Where they are intended for nitro-cellulose I may spray itself which then will become 'nitrated in the process. This may be done by beating cellulose in water until it loses its fibrous form and becomes a gel of cellulose hydrate, well known in the paper making art. The water containing the cellulose hydrate may be used as the adhesive spray. One

percent of the total cellulose present as hydrate for adhesive purposes is sufi'icient for securing the desired effects.

The above process is practically a dry felting process, although any moistureor liquid, used in the adhesive spray may be afterward dried out. It

is termed a dry process because the fibers are in a dry condition when they are showered onto the table. There is also a wet-process of forming fibers into a similar type of mat. I do not mean that the mats are the same, but they are sufficient 1y alike so that they have some properties in com-. mon which make them useful in the" process of this invention. I refer to the wet foaming process described in the U. S. Bryant Patent No. 1,- 740,280.

In so preparing cellulose I may take chemical Wood pulp, such as the very short fibers of aspen. Aspen is an extreme example of shortness in commercially available cellulose fibers. Cotton is an extreme example of length in commercially available fibers. The process is nevertheless the same,

. and is in some respect advantageous, regardless of whether cotton or aspen cellulose is employed. The advantage, however, increases with increasingshortness of the fibers.

The invention will be described with reference to aspen pulp. It may be taken as wet pulp from a paper .mill process, as from the washed pulp taken from a bleacher, after bleaching, or it may be dried pulp. In either instance it may be formed into a slurry with water to contain about /2% pulp (dry weight). I add a foaming agent, such as saponin to the extent of 4% of the weight tated until a foam is formed, the liquid character being lost. The foam is allowed to drain, pref erably on a screen, and preferably in a sheet of foam on a screen. Some free water drains away, and this, with any of its saponin content may be used in another foaming process. The residual foam is quite stable and dries as a foam or lather, presenting intermeshed fibers, considerably separated from each other in an open porous strong resilient cushion. The process and product may be varied and is more perfectly described inethe 5 U. S.Bryant Patent No. 1,740,280.

Water containing the cellulose hydrate above described may be used as the liquid vehicle for tion process employed. a

The mixture is beaten, whipped or agi- 7 fibers in forming foam, and the adhesive union controlled by regulating the amount of cellulose hydrate present. A nitrocellulose, or other cellulose ester may be present, as in an emulsion of a solution of it, in order to increase adhesiveness. 5 In wet-forming of a mat, asby the foaming proc- V ess, no adhesive need be added for the reason that made, are capable of being compressed or packed,

so that they may be shipped, and upon receipt, be in suitable form to be esterified without further mechanical treatment to open up the mat to permit access of liquid or acid thereto. The spongy 20 "or resilient character causes it to maintain and present open channels for rapid flow of liquid into it, when it is introducedinto a liquid, such as a nitrating acid.

The mass, preferably as a sheet of /2 to 1 inch 25 in thickness may be used for nitration or other reactive process, both in large pieces or in small pieces such as /2 to 1 inch square. It is preferable to use the smaller pieces because agitation of the reacting mass is facilitated without the agi- 30 tator catching the larger masses and compressing them into a more solid mass While submerged.

A mechanical picker, or a cutter, may be used to tear or out small pieces from a large sheet or roll of the bibulous mass. 65

The foaming agent is left distributed in the dried lather, and where other material has been added to the mass as an adhesive, to aid it in retaining its resilient unitary, bibulous form, it also'is present. Suchmaterial is preferably one 40 which is contributory to the ultimate product. Saponin is both'a foaming agent and to some extent anadhesive. It is harmless in the nitration process. In all cases those skilled in the art must observe the compatibility of the foaming agent and/or adhesive, and the particular reac- Experience has shown that fibers of wood cellulose prepared in accordance with this invention more readily take up the acid than the fluffy amorphous incoherent mass described in the Wilson application referred to. It has also shown that the fibers are more readily separable from the acid. This latter advantage is believed to be due to the absence-of short or broken fibers 50 which are formed to some extent by the mechanical disintegration of dried lap board. There is little possibility of having hard nodules in the process of this invention because the fibers are in final distended form when the drying is ef- 6O fccted. With no nodules and. with no. out fibers the weight yield of product is greater in a nitration process, as there is less danger of losing short fibers in the waste acid when a centrifugal separation is eifeoted. With no nodules, and with the uniform and complete nitration which results from this invention, a better quality of product is assured. 7 Although I have referred particularly to nitra tion, I include other processes in which fibers are impregnated with a liquid for reaction therewith. In nitration the fibers remain, and uniformity of impregnation is desired for uniformity of reaction. In acetylation, with mixtures containing acetic acid and sulphuric acid, the fibers are dissolved, but prior to dissolution they become gelatinous. When the fibers are loosely felted in a unit, as herein described, the liquid quickly penetrates the unit and surrounds the fibers, so that the fibers are uniformly gelatinized and reacted upon. And furthermore, the spacing of the fibers in the unit prevents building up a gelatinous dam which might for a time exclude reacting liquid from reactive contact with other fibers.

In some processes of making cellulose derivatives, alkali cellulose is made by immersing the cellulose in caustic alkali, and then reacting on the alkali cellulose fibers with a gas or vapor. Mats or masses of alkali cellulose made by the present invention are easily penetrated by such reactive gases, and more uniform results are obtained, and such uses are contemplated. In the broadest aspect of the present invention the term fluid contemplates liquid as well as gas.

The nitration and acetylation reactions are not specifically essential steps in the invention viewed in its broadest aspect, but are merely exemplary of one part of the process. They are specifically advantageous examples wherein better results are obtained. Various modifications of the process may be made and are herein considered as falling within the scope of the invention as expressed in the appended claims.

I claim:

1. In the manufacture of cellulose derivatives from cellulose fibers, the steps of forming cellulose fibers, a volatile liquid, and a foaming agent into a foam, drying the foam whereby to form a bibulous distended porous fibrous mass, and subjecting the fibrous mass'to the action of a fluid reactive with said fibers.

2. In the manufacture of cellulose esters from cellulose fibers, the steps of forming cellulose fibers, a volatile liquid, and a foaming agent into a foam, drying the foam whereby to form a bibulous distended porous fibrous mass, and subjecting the fibrous mass to the action of an esterifying liquid.

3. In the manufacture of cellulose derivatives from cellulose fibers, the steps of forming cellulose fibers, water, and a foaming agent into a foam, drying the foam whereby to form a bibulous distended porous fibrous mass, and subjecting the fibrous mass to the action of a liquid reactive with said fibers.

4. In the manufacture of nitrocellulose from cellulose fibers the steps of forming cellulose fibers, a volatile liquid, and a foaming agent into a foam, drying the foam whereby to form a bibulous distended porous fibrous mass, and subjecting the fibrous mass to the action of a nitrating acid.

5. In the manufacture of cellulose acetate from cellulose fibers the steps of forming cellulose fibers, a volatile liquid, and a foaming agent into a foam, drying the foam whereby to form a bibulous distended porous fibrous mass, and subjecting the fibrous mass to the action of an acetylating liquid.

6. In the manufacture of nitrocellulose from cellulose fibers the steps of forming cellulose fibers, water, and a foaming agent into a foam, drying the foam whereby to form a bibulous distended porous fibrous mass, and subjecting the fibrous mass to the action of a nitrating acid. 5 7. In the manufacture of cellulose acetate from cellulose fibers the steps of forming cellulose fibers, water, and a foaming agent into a foam, drying the foam whereby to form a bibulous distended porous fibrous mass, and subjecting the 19 fibrous mass to the action of an acetylating liquid.

8. In the manufacture of cellulose derivatives from cellulose fibers, thesteps of forming cellulose fibers, a volatile liquid, a foaming agent, and 15 an adhesive selected from the group consisting of cellulose hydrate, nitrocellulose, and cellulose acetate, into a foam, drying the foam, whereby to form a bibulous distended porous fibrous mass with fibers adhesively united, and subjecting the 20 fibrous mass to the action of a fluid reactive with said fibers.

9. In the manufacture of cellulose derivatives from cellulose fibers, the steps of forming cellulose fibers, water, a foaming agent, and hydrated 25 cellulose as an adhesive, into a foam, drying the foam, whereby to form a bibulous distended porous fibrous mass with fibers adhesively united, and subjecting the fibrous mass to the action of a fiuid reactive with said fibers. 30

10. In the manufacture of cellulose derivatives from cellulose fibers, the steps of hydrating the cellulose fibers to form a quantity of hydrated cellulose to serve as adhesive, forming said hydrated cellulose fibers, water, and a foaming 35 agent, into a foam, drying the foam, whereby to form a bibulous distended porous fibrous mass with fibers adhesively united, and subjecting the fibrous mass to the action of a fluid reactive with said fibers. 40

11. In the manufacture of cellulose derivatives from cellulose fibers, the steps of forming cellulose fibers, a volatile liquid, a cellulose ester in solution as an adhesive, and a foaming agent, into a foam, drying the foam, whereby to form 45 a bibulous distended porous .fibrous mass with fibers adhesively united, and subjecting the fibrous mass to the action of a fluid reactive with said fibers.

12. In the manufacture of nitrocellulose from 50 cellulose fibers, the steps of forming cellulose fibers, a volatile liquid, nitrocellulose in solution as an adhesive, and a foaming agent, into a foam, drying the foam, whereby to form a bibulous distended porous mass with fibers adhesively united,

and subjecting the fibrous mass to the action of a nitrating agent.

13. In the manufacture of cellulose acetate from cellulose fibers, the steps of forming cellulose fibers, a volatile liquid, cellulose acetate in solution as an adhesive, and a foaming agent, into a foam, drying the foam, whereby to form a bibulous distended porous mass with fibers adhesively united, and subjecting the fibrous mass to the action of a nitrating agent.

WALTER F. HOFFMAN. 

